When adding wiring to an already existing building, it is often very difficult to pass the wiring through double thickness walls, particularly in cases where the walls are filled with some sort of fibrous insulation, and where the holes in the wall must be kept to minimal diameters just sufficient to pass the wiring. It is particularly difficult to pass small diameter cables, such as RG 59 coaxial cable, which has an outer diameter of approximately 1/4". In an insulated wall the end of the cable tends to pick up the fibrous insulation and form a ball thereof which usually prevents passage of the cable all the way through the wall.
The present invention seeks to provide improvements over known grappling implements by providing a cable puller particularly well adapted for the purpose set forth above.
The prior art shows many examples of grappling devices employing two or more spring wire fingers which are permitted to separate when a sleeve is retracted on a stem so as to expose a greater length of finger, but which fingers are clamped together at their ends when the sleeve is moved along the stem so as to cover part of the length of the fingers and force their ends together.
Examples of such implements are included in Worthington U.S. Pat. No. 714,989 which shows a grappling device for recovering a well drilling tool from a well bore.
Patents such as Brandenberger U.S. Pat Nos. 1,578,800, Devareaux 2,212,013 and Rueckert 1,168,115 all show tools having multiple spring fingers with inwardly hooked ends.
U.S. Pat. Nos. 719,707 to Williams shows a tool in which the outer surface of the sleeve is tapered, which might make it easier to pull it through a double wall filled with fibrous insulation if it weren't for the blunt end 6 of the instrument.
However, none of these tools in its present form would be suitable for the purpose stated for the present invention, because none of them provides adequate enclosure of the entire end of the cable if the tool were used to pull a cable. One of the features of the present invention is that when the cable is locked to the present pulling tool, the sleeve covers a substantial portion of the length of the cable, leaving none of it, and none of the spring fingers, exposed to snag on the fibrous wall insulation, or on edges of a hole or other objects in the wall through which the cable is being pulled.